A ZnO-based flexible high voltage thin film transistor (f-HVTFT) is fabricated on a plastic substrate. The f-HVTFT shows a blocking voltage of 150 V, on-current of 170 μA, and off-current of 0.01 pA at a drain bias of 10 V. The maximum recoverable bending radius of the device reaches 11 mm, and the blocking voltage is larger than 120 V while it is under bending. The unique center-symmetric circular structure of the f-HVTFT is particularly useful to the wearable systems, which enable one to operate under bending from arbitrary directions. The ZnO-based f-HVTFT is a promising candidate to be used for power management of self-powered wearable electronic systems.